Endocytic proteins and the actin cytoskeleton: Project I concerns the function of the actin-based cytoskeleton in the vicinity of the neuronal synapse. The roles of Rac GTPases, the linking protein talin and dynamin in active zones will be explored. These studies will be complemented by studies on Src transformed cells, since these proteins are also found concentrated together with Src at sites of cell-substrate adhesion. Cortical ER inheritance in Saccharomyces cerevisiae: Project II concerns the segregation of the cortical endoplasmic reticulum (ER) in budding yeast. Through a primarily genetic approach, these studies will define the cytoskeletal track, the receptor on the cortex of the daughter cell and the protein that forms the link to the ER. Mechanisms of epithelial cell polarity: Project Ill concerns the relationship between membrane traffic in polarized epithelial cells with the spatial organization of the cytoplasm. Transport to basolateral and apical surfaces will be analyzed under conditions that affect critical steps. The role of specific vesicle associated proteins and target membrane associated proteins will be examined. The control of cell polarity by signaling proteins as well as kinases associated with new scaffold complexes will be explored. Cell polarity and the yeast secretory pathway: Project IV concerns the mechanism by which the Sec4p guanine nucleotide exchange protein Sec2p, becomes associated with secretory vesicles. The role of Sec2p, Sec4p and Ypt32p in the myosin dependent polarized movement of secretory vesicles to sites of secretion will be addressed. Partitioning of Golgi membranes during mitosis in animal cells: Project V concerns the mechanism by which the Golgi apparatus is partitioned during cell division. A variety of techniques will be used to determine if the Golgi itself is partitioned into daughter cells or if the Golgi is first recycled back into the ER, which is then partitioned. A possible cell cycle checkpoint for Golgi partitioning will be evaluated.